Age-resisting rubber composition and method of preparing same



Patented June 10, 1930 UNITED STATES PATENT OFFICE HAROLD W. ELLEY, OFWILMINGTON, DELAWARE AGE-RESISTING RUBBER COMPOSITION AND METHOD OFPREPARING SAME No Drawing.

This invention relates to a new rubber composition and to the method ofpreparing the same. More particularly it relates to a novel method forfortifying rubber against the deleterious effects of aging and to theresulting improved rubber product.

This application is a continuation in part of application Serial No.132,897, filed August 31, 1926.

It has been demonstrated that the deterioration of rubber products withage is probably due to oxidation. The incorporation of various materialshas been suggested for overcoming or mitigating this deterioration.

Such materials are referred to in United States Patents 1,496,792,1,515,642, 1,532,398 and 1,556,415. Moreover, additional informationrelative to the preservation of rubber products has been disclosed inGerman Patent 366,114 and in the British Patent 142,083.

In many cases the anti-aging materials are of no practical usefulnessbecause of various objectionable properties which they possess. Forexample, in some cases it is impossible to properly disperse thecompounds in the rub-,

er. Such uneven dispersion results in uneven aging and the well-knownspotting effects. In other instances, the anti-aging compounds have onlya mild effect in prevents in the oxidation and deterioration of the ruber. Moreover, the employment of many of the compounds so far suggestedis impractical on account of their high price.

One of the principal objects of the present invention, therefore, is toprovide an efiective anti-aging compound which may be evenly and quicklydispersed in the rubber. Another object is to provide an effectivecompound of this type which may be economically produced.

With these objects in view, it has been discovered that excellent agingproperties are imparted to rubber and similar substances by theincorporation therewith of certain secondary aromatic amines- Forexample, such compounds. as phenyl-alpha-naphthylamine and diphenylamineare of outstanding merit. Many other members of the class of disub- 5ostituted amines are also useful.

Application filed May 29, 1929; Serial No. 367,134.

The general procedure followed in employing members of this class ofcompounds may best be disclosed by specific examples which follow. .Itis to be understood that these. embodiments of the process are submittedby way of illustration only, and that the particular compounds andconditions therein specified are susceptible of variation within widelimits.

' Example 1 An anti-aging rubber composition containilngphenyl-alphanaphthylamine may be made according to the followingformula: Smoked sheets 50 Amber crepe 50 Zinc oxide; 121 Sulphur 1 2.75Diphenylguanidine 1 Phenyl-alpha-naphthylamine 1 This stock was-cured at141.5 C. for 30 minutes. It was then subjected to comparative tests, asto elongation and tensile strength, with a similar stock containing nophenyl-alpha-naphthylamine but cured to 76 the same degree under exactlythe same temperature conditions. After these tests, the two curedrubbers were submitted to accelerated aging tests in the Brierer-Davisoxygen bomb At the end of 24 hours they were 80 again tested. Theresults of the test are compared in the following table:

Prior to aging Ewample 2 l'part of diphenylamine was used instead of 1part of phenyl alpha-naphthylamine while maintaining the otheringredients and proportions employed in Example 1 constant. Theresulting stock was cured at 141.5 C. for 45 minutes and comparativetests made both before and after aging in the oxygen bomb for 24 hoursat C. and g2? lbs. pressure. The results are tabulated Prior to aging Itis obviousfrom the tabulated results of the tests that rubber stockscontaining the newly discovered anti-aging compounds possess markedlybetter aging properties than the stocks containing no such compound.Other secondary aromatic amines than those specified in the casesillustrated may be employed to impart anti-aging properties. For

example, in place of phenyl-alpha-naphthylamine or di henylamine, I maysubstitute di-tolyl amlneydi-xylyl amine or tolyl alpha-naphthylamine(the ortho, para or meta form of tolyl alpha-naphthylamine may beemployed). Likewise, meta xylyl or other xylyl substitutedalpha-naphthylamine may be employed, or if desired betanaphthyl groupsmay replace the corresponding alpha group in either the tolyl or xylylcompounds.

Also, it will be understood that my process is not limited to thetreatment of caoutchouc but is adapted for the treatment of substitutesas well, including balata and gutta-percha. I, therefore, employ theterm rubber in a generic sense.

The anti-aging compounds employed in the process are ordinarilyincorporated into the rubber mix during milling, but they may be appliedwith good eifect either before or after vulcanization by a procedureother than milling, as, for instance, in solution in suitable organicsolvents or in water if their solubility permits. Such solutions may beapplied to the surface of the rubber. It is also possible to expose therubber to vapors of these substances.

Likewise, the curing may be eifected by other methods than thosedisclosed, as, for example, by the well-known cold process. It is,therefore, not intended to limit the 1nvention to any particular methodof incorporating the reagent or curing the rubber.

The vulcanized rubber obtained as avresult 0f the process herein setforth is uniformly colored and does not spot. It possesses unusuallygood tensile strength, resistance to flexing and abrasion andexcellently withstands aging.

What I claim is:

1. A method of preserving rubber which comprises subjecting it tovulcanization in the presence of a naphthylamine containing an alkylsubstituted benzene group therein.

2. A method of preserving rubber which comprises subjecting it tovulcanization in the presence of a benzene substituted naphthylamine inwhich the benzene group contains at least one alkyl group.

3. A method of preserving rubber which comprises subjecting it tovulcanization in the presence of a material having the followingformula: RNR in which R is a naphthyl group and R is an alkylsubstituted benzene group, said material being substantially anon-accelerator of the rate of vulcanization of'the rubber.

4. A method of preserving rubber which comprises subjecting it tovulcanization in the presence of a material having the followingformula: R lR in which R is an alpha-naphthylamine group and R is analkyl substituted benzene group.

5. A method of preserving rubber which comprises subjecting it tovulcanization in the presence of a material having the followingstructural formula: RN-R in which R represents an alpha-naphthylaminegroup and R represents a tolyl group.

7. A rubber product that has been vulcanized in the presence of aIIInaterial having I the following formula: RNR in'which R represents anaphthyl group and R represents an alkyl substituted benzene group.

8. A rubber product that has been Vulcan ized in the presence of aEaterial having the following formula: R1l fR in which R i represents ana'phthyl group and R represent-s a tolyl group.

9. A rubber product that has been vulcanized in the presence of tolylnaphthyl'amine,

10., A rubber product that has been Vulcanized in the presence of tolylalpha naphthylamine.

11., A rubber product that has been vulcanized in the presence of amaterial having corporating with a rubber stock which con- H thefollowing formula: R-li-R in which R represents a naphth'yl group and Rrepresents a tolyl group.

12. The process of producing an age resisting rubber composition whichcomprises intains a vulcanizing agent, a di-substituted amine containingan alkyl substituted phenyl group and vulcamzing.

13. A process of producing an age resisting rubber stock compositionwhich comprises incorporating with a rubber stock containing therequisite vulcanizing ingredients, an. amirlif of the type representedby the formula R-hi-R in which the radical R is selected from the classcomprising the benzene and 'naphthylene series R is an aliphatichydrocarbon substituted benzene group, s'ald material beingsubstantially a non-accelerator of vulcanization.

14, A rubber product that has been vulcanized in the presence of amaterial having H the formula R-Ii-R in which R is a radical selectedfrom a class comprising the .naphthylene and benzene series, and R is analkyl substituted benzene group, said material being substantially anon-accelerator of the 'rate of vulcanization,

In witness whereof, I have hereunto signedmy name Si tied at JacksonLaboratory, in the (301111 ty 0 Salem and State of New Jersey, this 15thday of May, 1929.

HAROLD We ELLEY,

